1. Field of the Invention
This invention relates to an improving system for a display, and particularly to a residual image improving system for a LCD.
2. Description of the Related Art
FIG. 1a shows an equivalent circuit of a LCD after it is powered off. As shown in FIG. 1a, after it is powered off, the terminal voltage of a LCD is recharged and reduced to 0 V. At this point, when the LCD""s switch S has a high impedance at which the terminal voltage of the LCD is 0 V, the charge (i.e. CLC) of the LCD cannot be recharged right away, thereby producing a residual image on the LCD. FIG. 1b shows another equivalent circuit of the LCD after it is powered off. In FIG. 1b, the circuit includes an equivalent resistance Roff and an equivalent capacitance CLCD. As shown in FIG. 1b, the terminals A and B of the circuit have no input power so that the voltages on both A and B are zero. However, because the power is supplied to the capacitance CLCD through the resistance Roff before the power is turned off, the capacitance CLCD has residual charge after the power is turned off. This is because the resistance Roff is too high to release the charge completely. Thus, a residual image effect shows up and it lasts for a period of time that cannot be accepted by consumers. Hence, improving the residual image effect is necessary. Typically, the improvement is made by the manufacturing processor. The resistance Roff is reduced during manufacturing so that the charge in the capacitance CLCD can be released. However, a problem in such a manner is that the current Ioff becomes higher when the resistance Roff is reduced according to the Ohmic Rule and incurs a current leakage during normal operation.
Therefore, an object of the invention is to provide a residual image improving system for a LCD, thereby effectively improving the residual image effect.
A further object of the invention is to provide a residual image improving system for a LCD, thereby resolving the current leakage in the typical manner.
To realize the above and other objects, the invention provides a residual image improving system for a LCD. The improving system includes: a power supply for providing an operating power; a voltage detector for detecting the voltage level of an external power by comparison to a predetermined voltage level under the operating power and producing a control signal by comparing the results; and a video and timing control unit for outputting a predetermined pattern to the LCD according to the control signal so as to improve the residual image effect.
Accordingly, the invention cannot only prevent the visual system of a human being from the influence of the residual image effect, but also resolve the current leakage by avoiding the resistance change that causes the current leakage in the typical manner, thereby improving the residual image effect.